I think if that goes in... from the first glance, I think you will see an increase the number of Clerics of Chauntea, Gwaeron Windstrom, Lurue, Malar, Mielikki, Shiallia, Silvanus, Ubtao, Thard Harr, Aerdrie Faenya, Fenmarel Mestarine, Baervan Wildwanderer, and Segojan Earthcaller. Some of them also have plant domain for Barkskin.

Just imagine all those Divine Power Shapachange EDM cleric builds you can have.

" I am no longer here, the elves of the Sword Coast are just far too horrible... "

At first glance I don't necessarily see this as a major issue. If you go plant domain you aren't getting STR domain which essentially can be under the effect of Divine Power for a full rest cycle. Barkskin is only +1 AC over what you get from an amulet and honestly Cleric doesn't need the AC anyway with freedom of movement+deathward+extended stonebody and regeneration as needed.

In any case, I think Domain Spells is something currently being worked on both from a lore and balance perspective.

Same with the Plant Domain you mention (or any of the 'strong' domains, really). They are all nice, but not really needed. A cleric is going to be powerful with the right considerations for play style, spell selection and domains regardless. While I would agree you can 'get by' with 3 extended/3 regular casts of Divine Power that is only giving you ~27 minutes between rests and rebuff sessions. Plenty for the rest timer, but personally the longer I can go between rebuffing, the better.

Point is I don't see such a rush of Plant domain deities being an issue.... If anything, it'll continue to be water domain that 'owns' character concepts in terms of top domain. Obviously those deities with both will have plant as a strong second domain, but it's not that strong (as I previously mentioned.) Heck, I consider woodland stride a better benefit than getting Barkskin, personally.

Destruction Domain has Storm of Vengeance as level 8 spell. Will I be able to have an extended Storm of Vengeance in game? I presume that the targets of the spell fail their reflex saves consistently, and thus it would deal about 630 damage on avarage per creature within the AoE.

Sun Domain has Elemental Shield as a level 5 spell. Combine Freedom of Movement, with Deathward, then cast Stonebody for 10/DR, apply Regeneration for 10 points of regeneration, and proceed to use Elemental Shield. Unless the mobs are immune to fire, or at least highly resistant to fire, the mobs will just kill themselves trying to kill the cleric.

" I am no longer here, the elves of the Sword Coast are just far too horrible... "